<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <div>This is content, and data is: <span id="data"></span></div>
    <button id="button">click me</button>
    <script>
      let index = 0;
      function doRequest() {
        let data = document.getElementById("data");
        data.innerText = "";
        // fetch每次在请求时，X-Test-Cache里的值都不一样
        fetch("/data", {
          headers: {
            "X-Test-Cache": index++,
          },
        })
          .then(function (resp) {
            return resp.text();
          })
          .then(function (text) {
            data.innerText = text;
          });
      }
      document.getElementById("button").addEventListener("click", doRequest);
    </script>
  </body>
</html>
